1. Field of the Invention
The invention concerns a device for clamping and releasing a tool having a tool shaft, the device including a tool receptacle having on its free end an open socket part of an electrically conductive material for receiving the tool shaft with frictional engagement, and with a ring or cylindrical coil shaped induction coil surrounding the socket part of the tool receptacle, which coil can be energized with a preferably high frequency alternating current.
2. Description of the Related Art
Devices of this type are intended to be used for example for clamping or releasing a tool in the form of a milling cutter or drill in the tool receptacle. For this, the tool receptacle is heated in the area of the socket part with the aid of the induction coil, so that the borehole of the socket part expands. The tool is then introduced via its shaft into the heating-enlarged receptacle. During the subsequent cooling of the socket part, the tool shaft is frictionally held in the borehole of the socket part which shrinks as it cools. The diameter of the tool shaft and the socket part are therein so selected, that upon cooling a form-fitting connection results which is fixed against rotation, and which is not released even due to centrifugal forces during rapid rotation. For de-tensioning, the socket part is warmed again via the induction coil, until the tool can be pulled out of the receptacle. The de-tensioning is only possible because the heating spreads from outside towards inwards, so that first the socket part is warmed, prior to the warmth reaching the tensioned tool part. Thereby it is achieved, that first the socket segment expands, so that the still cooler tool can be released out of the receptacle during de-tensioning. This however functions only when the employed tool has low thermal coefficient of expansion and/or low electrical conductivity, for example hardened metal or ceramic. In the case of employment of insertion tools made of tool steel, there are however always problems during de-tensioning.